Non-combustible lubricating fluid

ABSTRACT

PCT No. PCT/SU88/00139 Sec. 371 Date Mar. 19, 1990 Sec. 102(e) Date Mar. 19, 1990 PCT Filed Jul. 25, 1988 PCT Pub. No. WO90/01057 PCT Pub. Date Feb. 8, 1990.The present invention relates to non-combustible lubricating materials. A non-combustible lubricating fluid is proposed, containing polyacrylamide, water, as well as triethanolamine and sodium nitrite, the ratio of the components being as follows, in % by mass: -polyacrylamide 0.3-0.6 -triethanolamine 0.8-1.5 -sodium nitrite 0.1-0.3 -water the balance. -

FIELD OF THE INVENTION

The invention relates to lubricating materials and, more particularly toa non-combustible lubricating fluid.

STATE OF THE ART

Lubrication of bearings in turbine and hydraulic turbo-machine controlsystems require the use of a lubricating fluid which ensures fluidfriction with a preset thickness of the bearing fluid film between therotary and stationary parts of the bearing, reduces the friction, andprovides transmission of hydraulic pulses in devices of hydraulicturbo-machine control systems.

As said lubricating fluids mineral turbine oils are used in the worldpractice of operating turbo-machines (V. N. Kazansky, "Sistemy SmazkiParovykh Turbin", 1974, Energiya Publishers, Moscow, pp. 9, 208-211).

Mineral turbine oils, however, suffer from a serious disadvantage: theyare fire-hazardous and cause fire accidents at electric power plants.

Also widely known in the art are non-combustible lubricating fluidsbased on water, including water itself. Water, however, has a lowviscosity (1 cSt) and, as a result, the thickness of the bearinglubricating film in the hydrodynamic sliding-contact bearing proves tobe insufficient for a reliable separation of the friction surfaces,which causes their increased wear and destruction.

Non-combustible lubricating fluids are known in the art, comprisingwater and polyglycols (K. I. Ivanov (ed.), "Ognestoikie TurbinnyeMasla", 1974, Khimiya Publishers, Moscow, pp. 20-22). These fluids,however, are disadvantageous in that their viscosity at a presettemperature is not sufficiently stable in the course of time, so thatthey fail to provide stable operation of the turbo-machines. Polyglycolsused in said lubricating fluids are very short-supply additives.

Also known in the art is a non-combustible lubricating fluid, comprisingwater and polyacrylamide (SU, A, 168826). However, the viscosity of thiscomposition is also unstable in the course of time at a presettemperature. Furthermore, this fluid is very aggressive with respect tocarbon steels which are the main structural materials in the manufactureof bearings for turbines, of hydraulic systems of turbo-machine control,and the like.

DISCLOSURE OF THE INVENTION

The invention is based on the problem of improving the stability in timeof the temperature-viscosity characteristics of a non-combustiblelubricating fluid, while reducing the aggressiveness thereof, byintroducing novel components into the composition of said fluid and bychanging the quantitative ratio of the components thereof.

This problem is solved by that a non-combustible lubricating fluidproposed herein, comprising polyacrylamide and water, according to theinvention, also comprises triethanolamine and sodium nitrite, the ratioof the components being as follows (in % by mass):

    ______________________________________                                        polyacrylamide 0.3-0.6                                                        triethanolamine                                                                              0.8-1.5                                                        sodium nitrite 0.1-0.3                                                        water          the balance.                                                   ______________________________________                                    

The rate of corrosion of carbon steel under the effect of the prior artnon-combustible lubricating fluid (SU, A, 168826) and under the effectof the herein-proposed non-combustible lubricating fluid, measured undersimilar conditions and with similar concentrations of polyacrylamide(0.4% by mass is 0.34 mm/year and 0.0021 mm/year, respectively. Thus,the non-combustible lubricating fluid proposed herein is appreciablyless aggressive than said prior art non-combustible lubricating fluid.

The non-combustible lubricating fluid proposed herein has a viscositywhose time stability at a preset temperature is higher than that of theprior art lubricating fluid (SU, A, 168826).

The herein-proposed non-combustible lubricating fluid provides reliableoperation of turbo-machines, it is explosion- and fire-safe, and nospecial measures of human protection are required when handling it.

BEST WAY OF CARRYING OUT THE INVENTION

If the ratio of the components of the herein-proposed lubricating fluidis changed, the reliability of the turbo-machine operation will belowered.

The concentrations of polyacrylamide proposed herein are dictated by thefact that if the polyamide concentration is lower than theherein-specified, the viscosity required for the formation of ahydrodynamic lubricating layer having a sufficient thickness cannot beattained. If the polyamide concentration exceeds the herein-specifiedvalues, the viscosity will increase sharply, and the lubricating fluidwill become technologically unfavourable.

If the concentration of triethanolamine and NaNO₂ is lower than theherein-specified values, the time stability of the temperature-viscositycharacteristic of the non-combustible lubricating liquid is disruptedand the aggressiveness of the non-combustible lubricating fluid withrespect to carbon steels increases. An increase in the content oftriethanolamine and NaNO₂ above the values specified herein leads to areduction of the viscosity of the lubricating fluid proposed in thepresent invention. To ensure the required viscosity, it would benecessary to introduce an additional quantity of polyacrylamide, thisbeing economically unfavourable.

The polyacrylamide employed in the herein-proposed non-flammablelubricating fluid may be in the form of a gel (usually of a 8%concentration) or in the form of dry powder.

The herein-proposed lubricating fluid for turbo-machines is prepared inthe following manner. Triethanolamine and sodium nitrite are introducedinto water, the resulting mixture is stirred, polyacrylamide is thenadded thereto, and stirring is continued till the desired product isobtained.

For a better understanding of the present invention, examplesillustrating its embodiments are given hereinbelow.

EXAMPLE 1

A non-combustible lubricating fluid according to the invention,comprising the following components, in % by mass:

    ______________________________________                                        polyacrylamide  0.3                                                           triethanolamine 1.5                                                           sodium nitrite  0.1                                                           water           98.1                                                          ______________________________________                                    

The non-combustible lubricating fluid of the invention for radialbearings of 420 mm in diameter was prepared in the following manner.

Three tons of water were charged into a vessel, 55.5 kg oftriethanolamine and 3.7 kg of sodium nitrite were then added thereto,the contents were stirred, 72 kg of a 8% gel or 5.8 kg of dry powder ofpolyacrylamide were then added thereto, the resulting mixture was againstirred till the desired product was obtained.

The results of tests of the herein-proposed lubricating fluid, residingin measuring its kinematic viscosity in the working range of its servicetemperatures (25°, 50°, 70° C.) after passing the fluid through abearing for 10, 20, 30, and 40 days are presented in the Tablehereinbelow.

EXAMPLE 2

A non-combustible lubricating fluid according to the invention,comprising the following components, in % by mass:

    ______________________________________                                        polyacrylamide  0.6                                                           triethanolamine 0.8                                                           sodium nitrite  0.1                                                           water           98.5                                                          ______________________________________                                    

The herein-proposed non-combustible lubricating fluid was prepared andtested as described in Example 1. The results of the tests are presentedin the Table hereinbelow.

EXAMPLE 3

A non-combustible lubricating fluid according to the invention,comprising the following components, in % by mass:

    ______________________________________                                        polyacrylamide  0.6                                                           triethanolamine 0.8                                                           sodium nitrite  0.3                                                           water           98.3                                                          ______________________________________                                    

The herein-proposed non-combustible lubricating fluid was prepared andtested as described in Example 1.

The results of the tests are presented in the Table hereinbelow.

EXAMPLE 4

A non-combustible lubricating fluid according to the invention,comprising the following components, in % by mass:

    ______________________________________                                        polyacrylamide  0.5                                                           triethanolamine 1.0                                                           sodium nitrite  0.2                                                           water           99.3                                                          ______________________________________                                    

The herein-proposed non-combustible lubricating fluid was prepared andtested as described in Example 1. The results of the tests are presentedin the Table hereinbelow.

                                      TABLE                                       __________________________________________________________________________       Number of days                                                                during which                                                                  the lubricat-                                                                 ing fluid was                                                                 passed through                                                                        Kinematic viscosity                                                                             Test                                             Nos                                                                              the bearing                                                                           25° C.                                                                      45° C.                                                                     50° C.                                                                      70° C.                                                                     results                                          1  2       3    4   5    6   7                                                __________________________________________________________________________    1   0      16.24                                                                              11.85                                                                             9.52 6.32                                                                              No changes                                          10      16.21                                                                              11.72                                                                             9.55 6.30                                                                              in the state                                        20      16.30                                                                              11.78                                                                             9.50 6.35                                                                              of the surface                                      30      16.20                                                                              11.80                                                                             9.51 6.34                                                                              of the                                              40      16.19                                                                              11.97                                                                             9.54 6.30                                                                              bearing or                                                                    journal                                          2   0      19.13                                                                              13.28                                                                             10.25                                                                              7.12                                                                              No changes                                          10      19.00                                                                              13.21                                                                             10.15                                                                              7.00                                                                              in the state                                        20      19.25                                                                              13.31                                                                             10.27                                                                              7.15                                                                              of the surface                                      30      19.15                                                                              13.24                                                                             10.27                                                                              7.10                                                                              of the                                              40      19.17                                                                              13.20                                                                             10.25                                                                              7.07                                                                              bearing or                                                                    journal                                          3   0      16.97                                                                              12.01                                                                             9.70 6.65                                                                              No changes                                          10      16.94                                                                              12.10                                                                             9.72 6.68                                                                              in the state                                        20      16.92                                                                              12.08                                                                             9.67 6.70                                                                              of the surface                                      30      17.00                                                                              12.12                                                                             9.78 6.73                                                                              of the                                              40      17.01                                                                              12.13                                                                             9.81 6.75                                                                              bearing or                                                                    journal                                          4   0      19.61                                                                              14.39                                                                             11.53                                                                              7.85                                                                              No changes                                          10      19.65                                                                              14.38                                                                             11.58                                                                              7.95                                                                              in the state                                        20      19.59                                                                              14.40                                                                             11.55                                                                              7.81                                                                              of the surface                                      30      19.63                                                                              14.43                                                                             11.52                                                                              7.84                                                                              of the                                              40      19.60                                                                              14.41                                                                             11.50                                                                              7.82                                                                              bearing or                                                                    journal                                          Prior art non-combustible lubricating fluid                                   (SU, A, 168826)                                                                0         13.21                                                                              7.75                                                                              5.63 2.81                                                                              Attrition of                                     10         12.46                                                                              7.10                                                                              5.13 2.43                                                                              the babbit                                       20         11.00                                                                              6.92                                                                              4.85 2.11                                                                              surface.                                                                      Tests are                                                                     stopped.                                         __________________________________________________________________________

INDUSTRIAL APPLICABILITY

The present invention may find application in the field of lubricatingmaterials for bearings used in turbomachines and for hydraulic systemsof turbo-machine control, as well as for other similar units.

We claim:
 1. A non-combustible lubricating fluid comprisingpolyacrylamide and water, characterized in that it also comprisestriethanolamine and sodium nitrite, the ratio of the components being asfollows, in % by mass:

    ______________________________________                                        polyacrylamide      0.3-0.6                                                   triethanolamine     0.8-1.5                                                   sodium nitrite      0.1-0.3                                                   water               the balance.                                              ______________________________________                                    